Interpretive Summary: Knowledge of insect dispersal or movement within agricultural production systems is important for effective pest management. Insect dispersal is often studied using marked insects, but the marker must be easily and unambiguously detectable, and must not alter the behavior of the marked insects. Markers based on immunoproteins (specific proteins that can be chemically detected in minute quantities) possess these qualities, but are too expensive for large scale studies. ARS scientists at Maricopa, AZ found that three inexpensive and commonly available proteins (egg white, skim milk, and soy milk) were effective and durable markers of lady beetle adults when the markers were sprayed on alfalfa. Concentrations of each protein necessary to mark more than 90% of lady beetles by direct spray contact were identified, and the beetles also acquired the markers from sprayed alfalfa foliage. Further refinement of marking techniques using these inexpensive proteins will provide a valuable and widely-available methodology to facilitate large-scale studies of insect movement.

Technical Abstract:
A field study was conducted to test the marking efficiency of broadcast spray applications of protein marks on stationary (represented by cadavers) and free-roaming lady beetles, Hippodamia convergens Guérin-Méneville that were strategically placed in blooming alfalfa plots. The marks tested included three different concentrations of egg albumin from chicken egg white, casein from bovine milk, and trypsin inhibitor from soy milk. The cadaver and free-roaming beetle treatments served to measure the acquisition and retention of each protein treatment regime by direct contact with the spray solution and by residual contact with protein-marked residue on alfalfa, respectively. In addition, the vertical distribution of marking efficacy was determined by sampling alfalfa plant tissue and cadaver beetles that were located on the upper and lower portion of the plant canopy. The data indicated that the backpack spray apparatus was very effective at uniformly administering the various protein marks, regardless of the concentration, throughout the entire plant canopy. Also, the free-roaming beetles readily self-marked by contact exposure to protein-treated plants. We also identified concentrations of each protein type that will mark about 90% of the resident beetle population. Moreover, if a mark-capture type study only requires two unique protein marks, we determined that concentrations of 25% for egg white and 100% for bovine milk could be used to mark 98% of the population. Our results provide a significant step toward standardizing protein immunomarking protocols for insect mark-capture dispersal research. In addition, we identify several areas of research that are needed to further standardize the protein mark-capture procedure.